The present invention relates to a method for color-developing a silver halide photographic light-sensitive material (hereinafter referred to as `light-sensitive material`), particularly to a novel method for developing a light-sensitive material, which not only is little affected by the bromide ion concentration fluctuation caused by changes in the replenishing quantity and the influence of the evaporation of a processing solution as well as by the processing time but also by no means impair the rapidness of processing; which is capable of forming a highly preservable dye image excellent in the resistance against discoloration by light; and which produces little or no magenta color stain due to the mixing in of heavy-metallic ions, and more particularly to a developing method which can be highly stably effected, being replenished with a small amount of a replenisher.
The processing of a light-sensitive material consists basically of two processes: color developing process and desilvering process, and the desilvering process consists of bleaching and fixing processes or of a bleach-fix process. Besides, the processing includes some other additional processess such as rinsing process, stabilizing process, and the like.
In a color develoment, an exposed silver halide is reduced to become silver, and at the same time the oxidized product of an aromatic primary amine developing agent reacts with a coupler to form a dye. In this process, the halide ion produced in the field of the silver halide is dissolved out into the developing solution used and accumulated therein. Aside from this, components such as a development restrainer, etc., contained in the silver halide photographic light-sensitive material is also dissolved into the color developer solution and accumulated therein. In the desilvering process, the silver produced by the development is bleached by an oxidizing agent, and then all the silver salt is turned by a fixing agent into a soluble silver salt to be removed from the light-sensitive material. In addition, a monobath bleach-fix process that effects the bleaching process and fixing process simultaneously is also known.
In the color developer solution, as is afore-mentioned, such development restraining materials are gradually accumulated as a result of the development of the photographic light-sensitive material, while the color developing agent and benzyl alcohol are consumed or accumulated into the photographic light-sensitive material and carried out along with the light-sensitive material, so that the concentrations of these components become lowered. Accordingly, a developing process for continuously processing a large quantity of silver halide photographic light-sensitive materials by an automatic processor requires a means for maintaining each of the components of the color developer solution in a given concentration range in order to avoid changes in the finished characteristics by changes in the concentrations of the components. Usually used as such means is a method for replenishing the developer solution with a replenisher for the purpose of making up for the shortage of the consumed components and diluting and undesirably increased components. However, the replenishment causes necessarily a large amount of overflows and discharges of the developer solution, so that the method has now become a vital issue from the economical and environmental pollution point of view. Accordingly, in order to lessen the amount of the above-mentioned overflow, the use of a smaller amount of a concentrated replenisher, i.e., the high-concentration/low-replenishment method, has become popular, and aside from this, a method for adding a recycling agent to the overflow liquid to reuse the liquid as a replenisher has been proposed and now made practical reality.
The above-described methods are for substantially reducing the replenishing quantity. If the replenishing quantity is extremely reduced, the concentrations of the organic restrainer and halide ions being dissolved out into the developer solution are to be largely affected not only by only a small error in the replenishing quantity but also by the condensation of the solution due to its evaporation, thus usually resulting in the increase in the concentration of the foregoing exhaust accumulation. For example, such phenomena result in the problems that the increase in the halide ion concentration restrains the developing reaction, and the foot portion of the characteristic curve of the light-sensitive material being restained thereby results in the formation of an extremely high-contrast image. In order to avoid this, a method has been proposed which is such that the halide ion is removed from the overflow liquid by use of an ion exchange resin of electrodialysis and then to the liquid is added a recycling agent for making up for the shortage of the components consumed by development or in the recycling process to thereby reuse the liquid as a replenising liquid.
The recycling by such an ion exchange resin or electrodialysis and the high-concentration/low-replenishment method have the disadvantage that they are subject to the influence of evaporation or of the recycling operation and undergo the change in the bromide ion concentration, and besides, the difference in the processing quantity of the light-sensitive material, particularly the difference between the beginning of week in which the number of processing orders increases and the weekend in which the number of processing orders decreases or between the high season and the off season, appear to the extent of up to a proportion of 1:5, and in addition they are also affected by the difference in the replenishing quantity as well as by evaporation, thus causing the composition of the developer solution to become largely differed.
Therefore, in the low-replenishment method and the recycling method an effort should be made to maintain the composition constant by conducting a quantitative analysis each time of recycling, but practicing the recycling or low-replenishment process may be, in most cases, be difficult for those processing labs or small-scale photofinishers having no special skill for the analysis.
The foregoing problems are due mainly to changes in the bromide ion, a development restrainer. To improve this, for example, there have been those proposals to reduce the silver bromide content of the photographic light-sensitive material to thereby decrease the accumulated amount of bromide ions or to lessen the bromide ion concentration's fluctuation due to evaporation or to an error in the replenishing quantity (as described in Japanese Patent Publication open to Public Inspection [hereinafter referred to as Japanese Patent O.P.I. Publication] Nos. 173189/1984 and 205540/1984).
Such problems may be expected to be solved, e.g., by improving the developability through making smaller the average grain size of the silver halide contained in the photographic light-sensitive material or lowering the coating amount of silver. However, in a color developer solution containing a conventional developing agent 3-methyl-4-amino-N-ethyl-N-.beta.-methanesulfonamidoethyl-aniline, if the developability is improved, the development, on the contrary, is easily affected by the fluctuation of the bromide ion concentration in the developer, impairing the processing stability, thus giving the results contrary to the expectation.
Nevertheless, it is essential that the processing stability is to be raised after the processing time is shortened.
A conventional processing of a color photographic paper comprised substantially of silver chlorobromide emulsions comprises color developing at 33.degree. C. for 3 minutes and 30 seconds, bleach-fix at 33.degree. C. for one minute and 30 seconds, washing for 3 minutes (or stabilizing for 3 minutes), and drying, totalling about 8 minutes, which is regarded as usual processing period. Although the strong needs of the times lie in the foregoing low-replenishment process from the economical point of view, the short-period processing is also strongly demanded from the standpoint of shortening the period for delivery.
However, as has been mentioned, the expeiditing and the stabilizing of the processing or the low repenishment are reciprocal problems, which have trade-off relations.
That is, if the development is made with low replenishment, the concentration of the bromide ion as a restrainer and the concentration of a sulfur compound or mercapto compound as an emulsion stabilizer increase to impair not only the rapidness but also the stability of the development.
However, various attempts have hitherto been made to expedite the color development. Particularly the foregoing developing agent, which has long been used as the most suitable agent for the development of silver chlorobromide emulsions, is slow in the permeation into the light-sensitive material because of its low hydrophilicity. In order to quicken the permeation, various types of permeating agent have been investigated, and as a result, for example, a method for expediting the color development by the addition of benzyl alcohol to a color developer solution has now been extensively used. This method, however, has the disadvantage that as long a development time as more than three minutes at 33.degree. C. is required for an adequate color formation, and besides, the development is subject to the delicate influence of the bromide ion concentration. Increasing the pH of the color developer solution is also known as the method for improving the permeability, but it is disadvantageous in respect that, if the pH exceeds 10.5, the oxidation of the color developing agent is extremely accelerated, and the development becomes easily affected by changes in pH because of no suitable buffer available, and thus becomes unable to give any stable photographic characteristics or dependent largely upon the processing time.
Increasing the quantity of the color developing agent in the color developer solution to raise the activity thereof is also known, but makes the developer solution costly because the developing agent is much expensive, and at the same time produces such instability that the foregoing agent is less soluble and is prone to be deposited, and thus cannot be used practically.
On the other hand, other methods are known which, in order to carry out the speeding up of the color development, in advance incorporates a color developing agent into the light-sensitive material, for example, a method which incorporates a color developing agent in the form of a metallic salt thereof into the light-sensitive material is known (as described in U.S. Pat. No. 3,719,492). This method, however, is poor in the preservability of the light-sensitive material, and has the disadvantage that it is fogged before use or otherwise prone to be fogged in the course of the color development process.
Further, those methods (as described in U.S. Pat. No. 3,342,559 and Research Disclosure, 1976, No. 15159) which incorporate into the light-sensitive material a color developing agent, for example, in the form of a Schiff's salt in order to inactivate the amine portion thereof are also known. However, such methods have the disadvantage that the color developing agent can not start its color development until after its alkali hydrolysis, and on the contrary the method retards the color development.
Further, the direct incorporation of a color developing agent into the light-sensitive material has the disadvantage that the emulsion thereof tends to be fogged during the storage thereof due to the instability of the color developing agent, and in addition the incorporation causes various processing troubles due to the emulsion layer's physical quality weakened by the agent.
In addition, the acceleration of development by the addition of a 3-pyrazolidone compound to a black-and-white developer solution containing a developing agent such as hydroquinone is known (as described in, e.g., L.F.A. Mason, `Photographic Processing Chemistry` p. 103-107, published by Focal Press, 1966). The fact of incorporating the compound into the light-sensitive material is described in British Pat. No. 767,704. However, the techniques described in the above patent specification are of the incorporation of the compound into a black-and-white light-sensitive material or into a reversal color light-sensitive material, the purpose of which incorporation is to accelerate the black-and-white image alone of such light-sensitive materials. And Japanese Patent O.P.I. Publication No. 52422/1978 describes the incorporation of a 3-pyrazolidone compound into a light-sensitive material for the purpose of preventing the deterioration of the sensitivity of an unexposed color light-sensitive material containing a two-equivalent magenta coupler having in the active site thereof an oxy-type organic split-off group. These techniques, however, are not applicable to such the speeding-up method characterized by stabilizing the color development in the low-replenishment system.
In order to expedite the color development by using conventionally known accelerating agents, these compounds have been investigated which are described in U.S. Pat. Nos. 2,950,970, 2,515,147, 2,496,903, 4,038,075 and 4,119,462, British Pat. Nos. 1,430,998 and 1,455,412, Japanese Patent O.P.I. Publication Nos. 15831/1978, 62450/1980, 62451/1980, 62452/1980 and 62453/1980, and Japanese Patent Examined Publication Nos. 12322/1976 and 49728/1980, and the like, but most of these compounds showed inadequate acceleration effects and the remaining showing high-acceleration effects not only had the disadvantage of producing a fog but were unsuitable for improving the processing stability.
The acceleration of the development by providing a silver halide emulsion layer substantially not light-sensitive in the light-sensitive material is known through the descriptions of Japanese Patent O.P.I. Publication Nos. 23225/1975 and 14236/1981, British Pat. No. 1,378,577, West German OLS Pat. No. 2,622,922, and the like. The function of the emulsion layer is to adsorb development inhibitors such as the useless halogen and useless split-off groups from the DIR couplers, DAR couplers, and the like, which all are released during the development, and is not to positively accelerate the developement, so that the emulsion layer showed little acceleration effects and no processing stability at all against the fluctuation of the bromide ion concentration, although it showed some effects against the fluctuation of the iodide ion concentration.
On the other hand, the color developing rate is said to be different according to the type of paraphenylenediamine derivatives used and to depend upon the oxidation-reduction potential of the developer solution used. Among such color developing agents the less-soluble-in-water-type color developing agent N-alkyl-substituted such as N,N-diethyl-p-phenylenediamine sulfate, 3-methyl-4-amino-N,N-diethylaniline hydrochloride, or the like, although highly active in development and capable of accelerating development, is known to be undesirable because of the low dark-discoloration characteristic of the formed dye therefrom after processing. Meanwhile, the 3-methyl-4-amino-N-ethyl-N-.beta.-methoxyethylaniline-di-p-toluene sulfonate (described in U.S. Pat. Nos. 3,656,950 and 3,658,525) said to be favorable in respect of being highly active in development is certainly excellent in the acceleration but is not suitable for use in the rapid developing process because of the disadvantage thereof that it has no ability to stabilize the bromide ion concentration and produces a significant yellow stain in the unexposed area of the processed photographic light-sensitive material; particularly the color developing agent remains when a short-period development took place and thereby causes a coarse stain.
On the other hand, 3-methyl-4-amino-N-ethyl-.beta.-methanesulfonamidoethylaniline-sesquisulfa te-monohydrate and 3-methyl-4-amino-N-.beta.-hydroxyethylaniline sulfate, etc., having a water-soluble alkylsulfonamido or hydroxyalkyl group-introduced N-alkyl group, as is described in Photographic Science and Engineering vol. 8, No. 3, May-June 1964, p. 125-137, have been said to be not so much different in the half-wave potential showing oxidation-reduction potential and to be both weak in the development activity.
Accordingly, there are few or no color developing agents being substantially active in the development of a silver chlorobromide emulsion and excellent in making the resulting dye image stable in aging, and in general, the foregoing purpose has been accomplished to date only by the use of 3-methyl-4-amino-N-ethyl-N-.beta.-methanesulfonamidoethylaniline sulfate along with benzyl alcohol.
In this instance, however, the development is subject to the influence of the change in the bromide ion concentration as previously stated. And the high-concentration/low replenishment processing using a reduced amount of a replenisher has another problem of the increase in the accumulation by the mixing in of other processing liquid components. This is because the renewal rate of the tank liquid by the replenisher is lowered due to the reduced quantity of the replenisher and also because the using period of the liquid is elongated. The mixing in of other liquid components is brought about by the splash of the adjacent liquid inside a processor, or the carrying of the processing liquid components immediately after development into the color developer solution by the film transport leader, belt or film hanger, etc.,; i.e., the so-called `back contamination`. Of such accumulated mixed-in components the thiosulfate ion as the fixing agent functions as a development accelerator. That is, this problem strongly occurs particularly when the light-sensitive material is processed in a bleach-fix bath immediately after color development. Especially, the mixing in of the thiosulfate ion accelerates the development of the shoulder portion of the photographic characteristic curve to thereby form a significantly high-contrast image. And the increase in the mixing in of a metallic salt, particularly a ferric salt, accelerates the decomposition of hydroxylamine as a preservative to thereby produce ammonia ions. The decomposition reaction is largely accelerated at a temperature above 30.degree. C. The ammonia ion, similarly to the thiosulfate ion, has the disadvantage of accelerating physical development to form a significantly high-contrast image.
For the above reasons, it is the status quo that realization of an improved color developer solution is strongly demanded which is capable of rapidly processing by being replenished with only a small amount of a replenisher; capable of maintaining the photographic characteristics of a light-sensitive material constant; and also capable of stably processing a light-sensitive material without decomposition of the components and change in the photographic processing characteristics even when used over an extensive period of time.